Hi, I presume the floating point code has been tested and works, in my experience people don't release code that that has not been tested, but of course a bug occasionally creeps in...
Without running your code it would seem to me that the code and your hardware behaves correctly when it is showing all LEDs of ie the value is zero. What you are attempting and assuming that -1 + 2 gives 1, but this presumes that -1 and 2 are presentable *exactly* in 'float' format, which is not the case, I think. So -1 + 2 is ever so slightly less than 1 which when truncated (cast to char) becomes 0 hence all the LEDs are off. You may want to study floating point math a bit more, it is full of pit falls like that, all too easy to step into one. br Kusti > From: Juan Gonzalez Gomez <[email protected]> > Reply-To: <[email protected]> > Date: Mon, 6 Apr 2009 03:00:07 +0300 > To: <[email protected]> > Conversation: [Sdcc-user] pic14: floating point error > Subject: [Sdcc-user] pic14: floating point error > > Hi, > > I am trying the sdcc 2.9.0 for the PIC16F876A device. I have found > that the floating point operations are not working well when negative > numbers are used. > > The following example works ok: > > #include <pic16f876a.h> > #include <float.h> > > volatile float test; > > void main(void) > { > TRISB=0x00; > > test=1; > PORTB=(unsigned char)(test+2); > > while(1); > } > > There is an 8-led board connected to the port B. When this program is > executed the number 3 (in binary) is shown. > > But if the test variable is assigned to the number -1, it does not work. > The following code does not work. The number 1 should be showed, but all > the leds are off > > #include <pic16f876a.h> > #include <float.h> > > volatile float test; > > void main(void) > { > TRISB=0x00; > > test=-1; > PORTB=(unsigned char)(test+2); > > while(1); > } > > If the test variable is declared as int, it works. So, it seems there > is a problems with negative floating points. > > The program is compiled like this: > > sdcc -Wl-m -Wl-ainhx8m -mpic14 -p16f876a -o float-error float-error.c > > Is this a known bug? Has anyone tested the floating point support for > the pic14? > > Thanks > > Best regards, Juan > > > -- > Juan Gonzalez Gomez > Blog: http://www.iearobotics.com/blog/ > Web : http://www.iearobotics.com/juan > > > ------------------------------------------------------------------------------ > _______________________________________________ > Sdcc-user mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/sdcc-user ------------------------------------------------------------------------------ _______________________________________________ Sdcc-user mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/sdcc-user
